It is well known that an excellent choice for light control is via the use of mirrors. Mirrors provide high reflectivity over broad bandwidths, as desired in WDM systems. Today, an excellent method for making actively controlled mirrors is via microelectromechanical system (MEMS) technology that promises to offer low cost compact optical modules via the use of low cost batch fabrication techniques similar to semiconductor electronic chip production methods. MEMS technology has been previously proposed to realize fiber optic beam control modules.
Various FO switches have been proposed using optical MEMS technology. The include 2×2 structures, wavelength add-drop (A-D) filters, and N×N crossconnects. For example, 2×2 type switches have been described in M. F. Dautartas, A. M. Benzoni, Y. C. Chen, G. E. Blonder, B. H. Johnson, C. R. Paola, E. Rice, and Y.-H. Wong, “A silicon-based moving-mirror optical switch,” Journal of Lightwave Technology, Vol. 10, No. 8, pp. 1078-1085, August 1992; and N. A. Riza and D. L. Polla, “Microdynamical fiber-optic switch,” U.S. Pat. No. 5,208,880, May 4, 1993, FO switches are proposed using the electronically controlled actuation of a single micromirror fabricated using micromaching techniques used in MEMS chip fabrication. More recently, others have used this “single micromirror per optical beam” control approach to realize 1×N and 2×2 switches. These works using MEMS or other mechanical means are described in W. J. Tomlinson and R. E. Wagner, “Optical switch,” U.S. Pat. No., 4,208,094, Jun. 17, 1980; H. J. Ramsey and M. L. Dakss, “Piezoelectric optical switch,” U.S. Pat. No., 4,303,302, Dec. 1, 1981; T. Tanaka, Y. Tsujimoto, H. Serizawa, and K. Hattori, “Optical switching device,” U.S. Pat. No. 4,304,460, Dec. 8, 1981; J. -P. Laude, “Switching device between optical fibers,” U.S. Pat. No. 4,484,793, Nov. 27, 1984; F. H. Levinson, “Optical coupling device utilizing a mirror and cantilevered arm,” U.S. Pat. No. 4,626,066, Dec. 2, 1986; G. E. Blonder, “Radiation switching arrangement with moving deflecting element,” U.S. Pat. No. 4,932,745, Jun. 12, 1990; A. M. Benzoni, “Magnetic activation mechanism for an optical switch,” U.S. Pat. No. 5,042,889, Aug. 27, 1991; G. A. Magel and T. G. McDonald, “Optical switch using spatial light modulators,” U.S. Pat. No. 5,155,778, Oct. 13, 1992; G. A. Magel, “Fiber optic switch with spatial light modulator device,” U.S. Pat. No. 5,199,088, Mar. 30, 1993; J. J. Pan, “1×N Electromechanical optical switch,” U.S. Pat. No. 5,359,683, Oct. 25, 1994; M. Ghezzo, C. P. Yakymyshyn, and A. R. Duggal, “Integrated microelectromechanical polymeric photonic switching arrays,” U.S. Pat. No. 5,367,584, Nov. 22, 1994; J. E. Ford, “Fiber optic switching device and method using free space scanning,” U.S. Pat. No. 5,621,829, Apr. 15, 1997; L. Yang, G. R. Trott, K. Shubert, K. Salomaa, and K. W. Carey, “Mechanical fiber optic switch,” U.S. Pat. No. 5,699,463, Dec. 16, 1997; T. G. McDonald, “Using an asymmetric element to create a 1×N optical switch,” U.S. Pat. No. 5,774,604, Jun. 30, 1998; J.-J. Pan, J.-Y. Xu, and C. J.-L. Yang, “Efficient electromechanical optical switches,” U.S. Pat. No. 5,838,847, Nov. 17, 1998; V. A. Aksyuk, D. J. Bishop, J. E. Ford, and J. A. Walker, “Freespace optical bypass-exchange switch,” U.S. Pat. No. 5,943,454, Aug. 24, 1999; V. A. Aksyuk, D. J. Bishop, and C. Randy, “Micro-machined optical switch with tapered ends,” U.S. Pat. No. 6,108,466, Aug. 22, 2000.
Other related works on switching includes E. Ollier, C. Chabrol, T. Enot, P. Brunet-Manquat, J. Margail, and P. Mottier, “1×8 Micro-mechanical switches based on moving waveguides for optical fiber network switching,” 2000 IEEE/LEOS International Conference on Optical MEMS, pp. 39-40, Kauai, Hi., August 2000; R. T. Chen, H. Nguyen, and M. C. Wu, “A high-speed low-voltage stress-induced micromachined 2×2 optical switch,” IEEE Photonics Technology Letters, Vol. 11, No. 11, pp. 1396-1398, November 1999; S. Nagaoka, “Compact latching-type single-mode-fiber switches fabricated by a fiber-micromachining technique and their practical applications,” IEEE Journal of Selected Topics in Quantum Electronics, Vol. 5, No. 1, pp. 36-45, January/February 1999; A. A. Yasseen, J. N. Mitchell, J. F. Klemic, D. A. Smith, and M. Mehregany, “A rotary electrostatic micromirror 1×8 optical switch,” IEEE Journal of Selected Topics in Quantum Electronics, Vol. 5, No. 1, pp. 26-32, January/February 1999; H. Toshiyoshi, D. Miyauchi, and H. Fujita, “Electromagnetic torsion mirrors for self-aligned fiber-optic crossconnectors by silicon micromachining,” IEEE Journal of Selected Topics in Quantum Electronics, Vol. 5, No. 1, pp. 10-17, January/February 1999; M. Makihara, M. Sato, F. Shimokawa, and Y. Nishida, “Micromechanical optical switches based on thermocapillary integrated in waveguide substrate,” Journal of Lightwave Technology, Vol. 17, No. 1, pp. 14-18, January 1999; S.-S. Lee, L. S. Huang, C.-J. Kim, and M. C. Wu, “Free-space fiber-optic switches based on MEMS vertical torsion mirrors,” Journal of Lightwave Technology, Vol. 17, No. 1, pp. 7-13, January 1999; C. Marxer and N. F. de Rooij, “Micro-opto-mechanical 2×2 switch for single-mode fibers based on plasma-etched silicon mirror and electrostatic actuation,” Journal of Lightwave Technology, Vol. 17, No. 1, pp. 2-6, January 1999; J. E. Ford and D. J. DiGiovanni, “1×N Fiber bundle scanning switch,” IEEE Photonics Technology Letters, Vol. 10, No. 7, pp. 967-969, July 1998; V. Aksyuk, B. Barder, C. R. Giles, R. Ruel, L. Stulz, and D. Bishop, “Low insertion loss packaged and fibre connectorised MEMS reflective optical switch,” Electronics Letters, Vol. 34, No. 14, pp. 1413-1414, July 1998; C. Marxer, C. Thio, M.-A. Gretillat, N. F. de Rooij, R. Battig, O. Anthamatten, B. Valk, and P. Vogel, “Vertical mirrors fabricated by deep reactive ion etching for fiber-optic switching applications,” Journal of Microelectromechanical Systems, Vol. 6, No. 3, pp. 277-285, September 1997; R. A. Miller, Y. C. Tai, G. Xu, J. Bartha, and F. Lin, “An electromagnetic MEMS 2×2 fiber optic bypass switch,” Transducers'97, pp. 89-92, Chicago, Ill., June 1997; S. S. Lee, E. Motamedi, and M. C. Wu, “Surface-micromachined free-space fiber optic switches with integrated microactuators for optical fiber communication systems,” Transducers'97, pp. 85-87, Chicago, Ill., June 1997; H. Toshiyoshi and H. Fujita, “Electrostatic micro torsion mirrors for an optical switch matrix,” Journal of Microelectromechanical Systems, Vol. 5, No. 4, pp. 231-237, December 1996; S. S. Lee, L. Y. Lin, and M. C. Wu, “Surface-micromachined free-space fibre-optic switches,” Electronics Letters, Vol. 31, No. 17, pp. 1481-1482, August 1995; L. A. Field, D. L. Burriesci, P. R. Robrish, and R. C. Ruby, “Micromachined 1×2 optical fiber switch,” Transducers'95, pp. 344-347, Stockholm, Sweden, June 1995; R. M. Boysel, T. G. McDonald, G. A. Magel, G. C. Smith, and J. L. Leonard, “Integration of deformable mirror devices with optical fibers and waveguides,” Proceedings of SPIE, Vol. 1793, pp. 34-39, 1992; K. Hogari and T. Matsumoto, “Electrostatically driven micromechanical 2×2 optical switch,” Applied Optics, Vol. 30, No. 10, pp. 1253-1257, April 1991; K. Hogari and T. Matsumoto, “Electrostatically driven fiber-optic micromechanical on/off switch and its application to subscriber transmission systems,” Journal of Lightwave Technology, Vol. 8, No. 5, pp. 722-727, May 1990.
Add-drop switches have also been proposed using MEMS. For instance, one such switching module is described in W. J. Tomlinson, “Wavelength-selective optical add/drop using tilting micromirrors,” U.S. Pat. No. 5,960,133, Sep. 28, 1999; J. E. Ford, J. A. Walker, V. Aksyuk, and D. J. Bishop, “Wavelength selectable add/drop with tilting micromirrors,” IEEE LEOS Annual Mtg., IEEE, N.J., postdeadline paperPD2.3, November 1997, where apart from the limitations of using a single micromirror per beam, this 4-port switch is not reversible and does not form a 2×2 switch that can be used to form larger N×N switch matrices. Other examples of add-drop switches using MEMS includes V. A. Aksyuk, B. P. Barber, D. J. Bishop, P. I. Gammel, C. R. Giles, “Micro-opto-mechanical devices and method thereof,” U.S. Pat. No. 5,995,688, Nov. 30, 1999; C. R. Giles, B. Barber, V. Aksyuk, R. Ruel, L. Stulz, D. Bishop “Reconfigurable 16-channel WDM drop module sing silicon MEMS optical switches,” IEEE Photonics Technology Letters, Vol. 11, No. 1, pp. 63-65, January 1999; V. A. Aksyuk, D. J. Bishop, J. E. Ford, R. E. Slusher, “Article comprising a wavelength selective add-drop multiplexer,” U.S. Pat. No. 5,974,207, Oct. 26, 1999; C. Pu, L. Y. Lin, E. L. Goldstien, R. W. Tkach, “Micro-machined optical add/drop multiplexer with client configurability,” 2000 IEEE/LEOS International Conference on Optical MEMS, pp. 35-36, Aug. 21-24, 2000. Similarly, in S. Glöckner, R. Goring, and T. Possner, “Micro-opto-mechanical beam deflectors,” Optical Engineering, Vol. 36, No. 5, pp. 1339-1345, May 1997; P. M. Hagelin, U. Krishnamoorthy, J. P. Heritage, O. Solgaard, “Scalable optical cross-connect switch using micromachined mirrors,” IEEE Photonics Technology Letters, Vol. 12, No. 7, pp. 882-884, July 2000; and L. Y. Lin, E. L. Goldstein, and R. W. Tkach, “Free-space micromachined optical switches with submillisecond switching time for large-scale optical crossconnects,” IEEE Photonics Technology Letters, Vol. 10, No. 4, pp. 525-527, April 1998, a single micromirror per beam that can be rather large in size is used, leading to slow millisecond range switching speeds.
Other mechanically implemented optical crossconnects are described in P. M. Hagelin, U. Krishnamoorthy, J. P. Heritage, O. Solgaard, “Scalable optical cross-connect switch using micromachined mirrors,” IEEE Photonics Technology Letters, Vol. 12, No. 7, pp. 882-884, July 2000; H. Laor, “Compact optical matrix switch with fixed location fibers,” U.S. Pat. No. 6,097,860, Aug. 1, 2000; O. Solgaard, J. P. Heritage, and A. R. Bhattaral, “Multi-wavelength cross-connect optical switch,” U.S. Pat. No. 6,097,859, Aug. 1, 2000; M. T. Fatchi and J. E. Ford, “Free-space optical signal switch arrangement,” U.S. Pat. No. 6,002,818, Dec. 14, 1999; R. L. Jungerman and D. M. Braun, “Optical cross-connect switch using a pin grid actuator,” U.S. Pat. No. 5,841,917, Nov. 24, 1998; F. H. Levinson, “Optical matrix switch,” U.S. Pat. No. 4,580,873, Apr. 8, 1986; G. J. G. Broussaud, “Optical switch for a very large number of channels,” U.S. Pat. No. 4,365,863, Dec. 28, 1982; T.-K. Koo, “Optoelectronic data entry means having plurality of control means to direct part of radiation in channel from radiation source to output channel,” U.S. Pat. No. 3,548,050, Mar. 7, 1972; D. T. Neilson, V. A. Aksyuk, S. Arney, N. R. Basavanhally, K. S. Bhalla, D. J. Bishop, B. A. Boie, C. A. Bolle, J. V. Gates, A. M. Gottlieb, J. P. Hickey, N. A. Jackman, P. R. Kolodner, S. K. Korotky, B. Mikkelson, F. Pardo, G. Raybon, R. Ruel, R. E. Scotti, T. W. Van Blarcum, L. Zhang, and C. R. Giles, “Fully provisioned 112×112 micro-mechanical optical crossconnect with 35.8 Tb/s demonstrated capacity,” OFC Technical Digest, Postdeadline, pp.PD12-1-PD12-3, Baltimore, Md., March 2000; H. Laor, J. D'Entremont, E. Fontenot, M. Hudson, A. Richards, and D. Krozier, “Performance of a 576×576 optical cross connect,” National Fiber Optic Engineers Conference, pp. 276-281, Chicago, Ill. September 1999; L. Y. Lin, E. L. Goldstein, J. M. Simmons, and R. W. Tkach, “High-density micromachined polygon optical crossconnects exploiting network connection-symmetry,” IEEE Photonics Technology Letters, Vol. 10, No. 10, pp. 1425-1427, October 1998.
Single pixel per beam MEMS-based variable FO attenuators have also been proposed such as described in J. E. Ford and J. A. Walker, “Dynamic spectral power equalization using micro-opto-mechanics,” IEEE Photonics Technology Letters, Vol. 10, No. 10, pp. 1440-1442, October, 1998, V. Askyuk, B. Barber, C. R. Giles, R. Ruel, L. Stulz, and D. Bishop, “Low insertion loss packaged and fibre connectorized MEMS reflective optical switch,” IEE Electronics Lett., Vol. 34, No. 14, pp. 1413-1414, Jul. 9, 1998, and B. Barber, C. R. Giles, V. Askyuk, R. Ruel, L. Stulz, and D. Bishop, “A fiber connectorized MEMS variable optical attenuator,” IEEE Photon. Technol. Lett., Vol. 10, No. 9, pp. 1262-1264, September 1998. Apart from the tolerance limited single pixel control approach, attenuation control in these modules is implemented in an analog fashion by carefully moving a micromirror per beam (or wavelength) through a continuous range of positions. For instance, in both the cited V. Askyuk, et.al. designs, a micromirror is linearly translated to partially block a beam and hence cause attenuation. In the J. Ford, et.al. design case, a micromirror is translated through many small sub-micron size steps to form a varying reflection surface, and this ultra-small motion makes the module very sensitive to vibrations. Thus, extensive module calibration and costly and complex control electronics are required to maintain the high performance of these analog-type FO MEMS-based modules. Other related works on mechanical or MEMS based VOAs are described in works such as V. A. Aksyuk, D. J. Bishop, P. L. Gammel, C. R. Giles, “Article comprising a light actuated micromechanical photonic switch,” U.S. Pat. No. 6,075,239, Jun. 13, 2000; E. E. Bergmann, D. J. Bishop, “Moving mirror switch,” U.S. Pat. No. 6,031,946, Feb. 29, 2000; P. Colbourne, J. Obhl, N. Teltelbaum, “Variable optical attenuator,” U.S. Pat. No. 5,915,063, Jun. 22, 1999; J. E. Ford, K. W. Goossen, “Level setting optical attenuator,” U.S. Pat. No. 5,900,983, May 4, 1999; C. M. Garrett, C Fan, D. Cugalj, D. Gransden, “Voltage controlled attenuator,” U.S. Pat. No. 5,745,634, Apr. 28, 1998; J. E. Ford, D. A. B. Miller, M. C. Nuss, J. A. Walker, “Attenuation device for wavelength multiplexed optical fiber communications,” U.S. Pat. No. 5,745,271, Apr. 28, 1998; R. Wood, V. Dhuler, E. Hill, “A MEMS variable optical attenuator,” 2000 IEEE/LEOS International Conf. on Optical MEMS, pp. 121-122, Kauai, Hi. 21-24 August 2000; K. W. Goossen, J. A. Walker, D. T. Neilson, J. E. Ford, W. H. Knox, “Micromechanical gain slope compensator for spectrally linear optical power equalization,” IEEE Photonic Technology Letters, Vol. 12, No. 7, pp.831-833, July 2000; F. Chollet, M. de Labachelerie, H. Fujita, “Compact evanescent optical switch and attenuator with electromechanical actuation,” IEEE Journal of Selected Topics in Quantum Electronics, Vol.5, No. 1, January/February, 1999; F. Chollet, M. de Labachelerie, H. Fujita, “Electromechanically actuated evanescent optical switch and polarization independent attenuator”, Proc. IEEE MEMS Conf., pp.476-481, 1998.
It is very important to note that all the above works cited in mechanically motivated and optical MEMS-related components or subsystems use the principle of “a single mirror element controls a single fiber-optic beam.” This is unlike the proposed embodiments in this application where a “Macro-pixel” or multiple mirrors controls a single optical beam.
Many advanced optical networking applications require subsystems that can simultaneously and independently control various parameters of an optical beam, such as amplitude level, time delay, and routing path. The need and method to accomplish parts of these tasks has been pointed out in such works as N. A. Riza, “High Speed Fiber-Optic Switch,” U.S. Pat. No. 6,282,336, issued Aug. 28, 2001, and in N. A. Riza and S. Sumriddetchkajorn, “Micromechanics-based Wavelength Sensitive Fiber-Optic Beam Control Structures and Applications,” Applied Optics, Vol. 39, No. 6, pp. 919-932, Feb. 20, 2000, and N. Antoniades, et.al., “Engineering the performance of DWDM metro networks,” NFOEC 2000 Conf. Proc., pp. 204-211, Denver, Aug. 27-31, 2000.
It is the purpose of this application to introduce FO processors that have the capability to independently and simultaneously accomplish these key tasks of controlling optical beam amplitude level and routing path on a per wavelength basis. It is also the purpose of this application to introduce a processor that accomplishes simultaneous broadcasting of optical signals to different ports of the switch. These processors are unique in their use of a digitally controlled FO module using optical MEMS-based macro-pixel devices to form compact and fault-tolerant multiwavelength structures to simultaneously accomplish the gain and routing beam processing tasks. Specifically, these processors and their beam control submodules incorporate the unique “macro-pixel” approach to beam controls that has been introduced by N. A. Riza in earlier works such as described in N. A. Riza, “Fault-tolerant fiber-optical beam control modules,” U.S. Pat. No. 6,222,954, issued Apr. 24, 2001; N. A. Riza and S. Sumriddetchkajorn, “Digitally controlled fault-tolerant multiwavelength programmable fiber-optic attenuator using a two dimensional digital micromirror device,” Optics Letters, Vol. 24, No. 5, pp. 282-284, Mar. 1, 1999; N. A. Riza and S. Sumriddetchkajorn, “Small tilt micromirror device-based multiwavelength three-dimensional 2×2 fiber-optic switch structures,” Optical Engineering, Vol. 39, No. 2, pp. 379-386, February 2000; and N. A. Riza and S. Sumriddetchkajorn, “Fault-tolerant dense multiwavelength add-drop filter with a two-dimensional digital micromirror device,” Applied Optics, Vol. 37, No. 27, pp. 6355-6361, Sep. 20, 1998. This application is the first disclosure of macro-pixels based on digital operation small tilt micromirrors coupled with a fiber collimator lens used simultaneously to accomplish the tasks of light routing and amplitude controls with broadcast capability. Specifically, it is shown how several processors for WDM signal controls can be devised using a macro-pixel based optical beam control module. The simultaneous yet independent routing and gain control attributes for any wavelength of proposed fault-tolerant processors make them a powerful conditioning tool for optical beams in WDM fiber-optic networks and is the subject of this invention.